Path: utzoo!utgpu!news-server.csri.toronto.edu!neat.cs.toronto.edu!mgreen
Newsgroups: comp.graphics
From: mgreen@cs.toronto.edu (Marc Green)
Subject: re: Psycho Graphics
Message-ID: <91Feb14.110238est.7256@neat.cs.toronto.edu>
Organization: Department of Computer Science, University of Toronto
Date: 14 Feb 91 16:02:53 GMT
Lines: 27

All this talk of "Psycho Graphics" shows that many computer graphics
people badly need a basic perception course. Why? Because there is
very little correlation between physics and perception.

Perception is psychological while images are physical. The
relationship between the two complicated and not deterministic. For
example, it is easy to make physically identical lights look different
and physically different lights look identical. The number of quanta
in a light and the wavelength play a surprisingly small role in the
way a light is perceived. The perception of motion, depth, size, etc.
likewise cannot be readily predicted from the physical properties of
an image alone. The mapping from images to perception cannot be
predicted without knowing a great deal about the visual system.

The basic fact to remember is that our perceptions are manufactured in
our heads and depend as much or more on the way our visual systems are
wired together than by the retinal image. It is wasted effort to spend
time worrying about complicated camera models and the like. For
example, fancy models of motion blur simply are unnecessary. The real
question is not how to make computer graphics look like cameras, but
why the blur improves motion perception in the first place. In fact,
quite a bit of psychophysical work has been done in this area if
anybody took the time to look for it in Vision Research, Perception,
or any other other journals concerned with human vision.

Marc Green